1) Field of the Invention
The present invention relates generally to vehicles with hydrostatic transmissions, such as lawn and garden tractors, and more specifically to a speed or cruise control for such a vehicle.
2) Related Art
Controls for an off-road vehicle having a hydrostatic transmission typically include a direction control level, or direction control pedals, along with some form of transmission speed ratio control which may be a separate lever or pedal or which may be combined with the direction control devices. With many transmission systems, a foot pedal is utilized to select speed ratio and must be continuously held in the desired position during operation of the vehicle. Maintaining the transmission in the desired speed ratio becomes difficult over extended periods of operation. Although numerous speed ratio controls have been available, most of the controls have suffered from one or more disadvantages. A number of the mechanically operated speed ratio controls required numerous parts such as additional linkages which add to the cost and complexity of the transmission system. Mechanical devices are often difficult to assemble and adjust; such devices can wear over time and not engage or hold a selected ratio properly. Electrically operated hydrostatic cruise controls have typically employed extra linkages or special electromagnetic clutches which require additional space on the vehicle and add complexity to the system. A relatively high holding force is necessary, and circular electromagnetic clutches have been utilized to maintain the desired control pedal position.